2-1/2-8 NPT vs 3-1/2-6NH: specs compared
Updated 05 September 2026.
107.77 mm
3-1/2-6NH wins on major diameter
On major diameter, 3-1/2-6NH leads: 107.77 mm versus 73.02 mm.
| Spec | 2-1/2-8 NPT | 3-1/2-6NH |
|---|---|---|
| Designation | 2-1/2-8 NPT | 3-1/2-6NH |
| Major diameter | 73.02 mm | 107.77 mm |
| Threads per inch / pitch | 8 | 6 |
| Thread form | tapered, 60 degree | straight (parallel), 60 degree |
| Seals on | on the thread flanks with PTFE tape | rubber gasket in the female swivel |
Questions and answers
Which has the higher major diameter, 2-1/2-8 NPT or 3-1/2-6NH?
On major diameter, 3-1/2-6NH leads: 107.77 mm versus 73.02 mm.
How do 2-1/2-8 NPT and 3-1/2-6NH compare?
On major diameter, 3-1/2-6NH leads: 107.77 mm versus 73.02 mm.